Continued progress with the establishment of mature Wuchereria bancrofti infections in macaque monkeys allows for further trials with the serial passage of this human parasite into other monkeys and thus hopefully provides a continuing laboratory source that will allow for further expansion of our transmission studies. Various aspects of the ultrastructural morphology of the infective-stage larva and the adult parasites of W. bancrofti will be completed. Studies on the immune response of the jird, Meriones unguiculatus, with Brugia pahangi will continue by utilizing an inbred strain of jird. Previous identification of an Fc receptor and a complement receptor, and current work at establishing an Ig marker will be part of a continuing study to establish functional subclasses of lymphocytes in filaria-infected jirds. Since it has proven possible to establish B. pahangi infections in mice, through the use of irradiation techniques, further trials at establishing patent filarial infections in this will enhance our studies on the immune response in a well defined animal host.